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Pilot plant studies of air flotation of oil refinery waste waters

page 368

Pilot Plant Studies of Air Flotation of
Oil Refinery Waste Waters
GERARD A. ROHLICH
Professor of Sanitary Engineering
University of Wisconsin
Madison, Wisconsin
Flotation as a method for the treatment of sewage and industrial
wastes has received increased attention during the past several years.
The use of flotation methods for the concentration of mineral ores
however has a history extending over almost a century. In mineral
flotation highly effective as well as highly selective separations have
been obtained with the use of specific flotation reagents.
Gaudin (8) summarizes the important steps in the development of
the process and presents the basic principles and their application to
the flotation of ores in the mineral industry. Early processes in this
industry were based on the use of oils to selectively attach themselves
to acidulated ground or pulverized ore. As early as 1901 the use of
gas as the buoyant medium was recognized, the gas being produced by
chemical reaction between the acid ore and suspended sulfides and carbonates. This development was followed by direct introduction of
gas by use of mechanical mixing or by diffusion of gas through porous
media or submerged pipes. The marked progress in the concentration
of ores by the flotation process has been made possible by the use of
chemical flotation reagents which act as frothers and/or collectors which
facilitate the attachment of the gas bubble to the solid particle. The
use of the proper reagent has made possible highly selective collection.
As might be expected, the principles of flotation have been applied
in other industries, such as the paper industry, where recovery of fibre
in white water systems is accomplished by flotation methods (4).
In the field of water purification Hopper (11) conducted experimental studies on 34 different raw water supplies. The results showed
average reduction in turbidity of 70 percent, reduction in suspended
solids of 79 percent, and bacterial reductions of 90 percent. In these
experiments Hopper added 20 p.p.m. of wetting agent (Roccal) to the
turbid water, followed by a 10 minute aeration period and skimming
off of the foam. These studies were followed by additional and more
extensive work by Hopper and McCowen (12) using quaternary ammonium compounds as the surface active agents. The results substan-
368

Pilot Plant Studies of Air Flotation of
Oil Refinery Waste Waters
GERARD A. ROHLICH
Professor of Sanitary Engineering
University of Wisconsin
Madison, Wisconsin
Flotation as a method for the treatment of sewage and industrial
wastes has received increased attention during the past several years.
The use of flotation methods for the concentration of mineral ores
however has a history extending over almost a century. In mineral
flotation highly effective as well as highly selective separations have
been obtained with the use of specific flotation reagents.
Gaudin (8) summarizes the important steps in the development of
the process and presents the basic principles and their application to
the flotation of ores in the mineral industry. Early processes in this
industry were based on the use of oils to selectively attach themselves
to acidulated ground or pulverized ore. As early as 1901 the use of
gas as the buoyant medium was recognized, the gas being produced by
chemical reaction between the acid ore and suspended sulfides and carbonates. This development was followed by direct introduction of
gas by use of mechanical mixing or by diffusion of gas through porous
media or submerged pipes. The marked progress in the concentration
of ores by the flotation process has been made possible by the use of
chemical flotation reagents which act as frothers and/or collectors which
facilitate the attachment of the gas bubble to the solid particle. The
use of the proper reagent has made possible highly selective collection.
As might be expected, the principles of flotation have been applied
in other industries, such as the paper industry, where recovery of fibre
in white water systems is accomplished by flotation methods (4).
In the field of water purification Hopper (11) conducted experimental studies on 34 different raw water supplies. The results showed
average reduction in turbidity of 70 percent, reduction in suspended
solids of 79 percent, and bacterial reductions of 90 percent. In these
experiments Hopper added 20 p.p.m. of wetting agent (Roccal) to the
turbid water, followed by a 10 minute aeration period and skimming
off of the foam. These studies were followed by additional and more
extensive work by Hopper and McCowen (12) using quaternary ammonium compounds as the surface active agents. The results substan-
368